地壳中气体运动的大尺度特征

Characteristics of Large-scale Gas Motion in the Earth's Crust

摘要:

地壳内流体的运动与地球动力学、地震、地球排气及气候变化等密切相关。本文利用我国239个气象站0~3.2 m地温资料，用3种方法计算了地气界面的年平均热通量，发现30°N以南的低纬地区表现为地热的净积累，30°N以北的中高纬地区为地热净放散，其量值达到2 W/m²，表明在岩石圈中有热量从低纬输向高纬，形成地气环流。岩石圈裂隙中地下流体（地气）的运行速度要达到10~30 cm/s才可完成热量的纬向输送。本文统计了2003-2007年中国大陆地热涡的逐月移动速度，发现以300~600 km/月（10~20 cm/s）为最多。

Abstract:

At present,it is still known less about the large-scale motion characteristics of fluid in the Earth's crust. The motion characteristics of fluid in the Earth's crust are close related to the geo-dynamics,earthquake,earth's degassing and climate change etc. In this paper,by using the multi-year observation data of soil temperature for different layers at 239 meteorological stations in China,we calculate the annual averaged heat flux over the interface between land and atmosphere with 3 methods and find that it has an opposite annual variation with latitude. a net heat absorption in the south area of 300N and a net heat emission in the north with a flux of 2 wm^-2,which demonstrates the heat flows transfer from low to high latitude in the lithosphere with causing an underground circulation as that in the atmosphere. Assuming that the porosity in the surface of lithosphere (z=0) is 10^-1 and 10^-5 in the bottom,10~30 cm/s speed is needed for underground fluid(gases in earth) to supply a meridional heat transfer. The statistic for the monthly moving rate of the geothermal vortex in the period of 2003 to 2007 is made in China. The results show that the 300~600 km rate of one month is the most common,the seismic vortex with MS≥7.0 can move backwards and the one with MS=6.9 can be taken as a "static vortex" with a 350 km distance of farthest precursor that is recognized as a semi-wave-length of the seismic vortex. Therefore,we can evaluate a mean speed of 20 cm/s for the underground gases with Rossby formula. So we can conclude that the underground circulation is also a three-cell circulation.